Immunological synapse

In immunology, an immunological synapse (or immune synapse) is the interface between an antigen-presenting cell or target cell and a lymphocyte such as an effector T cell or Natural Killer cell. It is the subject of much ongoing research.

The immune synapse is also known as the supramolecular activation cluster or SMAC. This structure is composed of concentric rings (often referred to as a bull’s eye model of the immunological synapse) each containing segregated clusters of proteins:

New investigations, however, have shown that the original bull’s eye model is not present in all immunological synapses. For example, different patterns appear in the synapse between T-cell and dendritic cell.

This complex as a whole is postulated to have several functions including but not limited to:

The initial interaction occurs between LFA-1 present in the p-SMAC of a T-cell, and non-specific adhesion molecules (such as ICAM-1 or ICAM-2) on target cell. When binded to the target cell, T-cell can extend pseudopodia and scan the surface of target cell to find a specific .

The process of formation begins when T-cell receptor (TCR) binds to the peptide:MHC complex on the APC. Specific signalization pathways lead to polarization of the T-cell by orientation of its centrosome towards the site of the immunological synapse. The symmetric centripetal actin flow lays at the basis of formation of the p-SNAP ring. Some parts of this process may differ in CD4+ and CD8+ cells.

The whole process of the immunological synapse formation takes about 6 hours.

It was first discovered by Abraham Kupfer at the National Jewish Medical and Research Center in Denver and the term was coined by Michael Dustin at NYU who studied it in further detail. Daniel M. Davis and Jack Strominger showed structured immune synapses for a different lymphocyte, the Natural Killer cell, and published this around the same time. Abraham Kupfer first presented his findings during one of the Keystone symposia in 1995, when he showed three-dimensional images of immune cells interacting with one another. Key molecules in the synapse are the T cell receptor and its counterpart the (MHC). Also important are LFA-1, ICAM-1, CD28, and CD80/CD86.

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Wikipedia